The flow rate of the pump, that is, the amount of water, generally should not be selected too large, otherwise it will increase the cost of purchasing water pumps. Should be selected on demand, such as the user's home use of self-priming pumps, the flow rate should try to choose some small; such as the user irrigation submersible pumps, you can choose the appropriate flow rate of some of the larger.
1) to buy water pumps according to local conditions. Commonly used agricultural water pumps have three types, namely centrifugal pumps, axial flow pumps and mixed flow pumps. Centrifugal pump head is higher, but the water is not large, suitable for mountainous areas and well irrigation; axial pump water is larger, but the head is not too high, suitable for use in the plains; mixed-flow pump water and head between centrifugal pumps and axial pumps, suitable for use in the plains and hilly areas. Users should choose and buy according to the ground conditions, water source and water lifting height.
2) to choose the appropriate standard pump. Determine the type of pump, to consider its economic performance, pay special attention to the head and flow of the pump and its supporting power selection. It must be noted that the head indicated on the pump label (total head) and the use of water head (actual head) is a difference, this is due to the flow of water through the water pipeline and piping near the time there will be a certain loss of resistance. Therefore, the actual head is generally lower than the total head of 10-20%, the amount of water is also reduced accordingly. Therefore, the actual use, only according to the labeling of the head and flow rate of 80% to 90% of the estimated power of the pump supporting the selection of power, according to the labeling on the power selection, in order to enable the pump to start quickly and the use of safety, the power of the power machine can be slightly larger than the pump power requirements, generally higher than the appropriate 10% or so; if there is already a power to buy a pump, the power machine can be purchased according to power and the power of the matching Water pump.
3) to strict procedures for the purchase of water pumps. When choosing to examine the "three certificates", that is, agricultural machinery promotion license, production license and product inspection certificate, only three certificates can avoid the acquisition of obsolete products and inferior products.
The number of units to choose
1, the normal operation of the pump, generally only one, because a large pump and parallel work of two small pumps, (referring to the head, flow rate is the same), the efficiency of the large pump is higher than the small pump, so from the energy-saving point of view would rather choose a large pump, but not use two small pumps, but in the case of the following circumstances, you can consider the two pumps in parallel to work together: the flow rate is very large, a pump to reach this flow.
2, for the need to have a 50% standby rate of large pumps, can be changed to two smaller pumps work, two standby (*** four)
3, for some large pumps, you can choose 70% of the flow requirements of the pumps operated in parallel, without the standby pumps, a pump overhaul, the other pump is still bearing the production of 70% of the delivery.
4, the need for 24-hour continuous operation of the pump, three pumps should be backed up, a running, a standby, a maintenance.
Parameter selection
Water supply pressurization station is to alleviate the shortage of urban water supply pressure of an effective measure, the core of which is to enhance the pumping station, and the core of the pumping station is the pump. Pump selection not only affects the water supply pressurization station can work properly, the selection of reasonable more directly related to the operating costs of the pumping station.
Domestic general water supply pressurization station is usually used centrifugal pumps, centrifugal pumps have a simple structure, infusion of pulsation-free, simple flow rate adjustment and other advantages. According to the actual situation of the project, first select the category of centrifugal pumps for the following considerations.
(1) according to the characteristics of the medium to decide which characteristics of the pump. Such as clear water pumps, corrosion-resistant pumps, or chemical process pumps and impurities pumps. Medium for highly toxic, valuable or radioactive substances are not allowed to leak, should consider the selection of non-leakage pumps (such as shielded pumps, magnetic pumps, etc.) or with a leakage collection leakage alarm device with a double-face mechanical seal. If the medium for liquefied hydrocarbons and other volatile liquids should be selected with low cavitation margin bungee, such as cylinder pumps.
(2) according to the site installation conditions to choose horizontal pumps, vertical pumps (including submerged pumps pipeline pumps).
(3) according to the size of the flow rate of single-suction pumps, double-suction pumps, or small flow centrifugal pumps.
(4) According to the head height of single-stage pumps, multi-stage pumps, or high-speed centrifugal pumps.
After the above items are determined, according to the various types of pumps in different series of pumps and the characteristics of the conditions of the production plant, select the appropriate pump series. Pump type, series and materials selected, and then according to the samples provided by the pump manufacturer and the relevant parameters to determine the pump model.